health4.ai — Apple Health × AI

Ask your AI about your sleep, HRV, recovery, and fitness — in plain language.
Free iOS app · Your own database · Works with any MCP client

Download health4ai on the App Store

What it does

iPhone HealthKit → Your Supabase project → MCP server → Any AI

Apple Health holds years of your biometric data — sleep stages, HRV, heart rate, workouts, VO₂ max, and 150+ other metrics. health4.ai makes all of it queryable from Claude, ChatGPT, Cursor, Ollama, or any MCP-compatible client through purpose-built MCP tools.

You control the data. It syncs to a Supabase project you create and own. health4.ai runs no backend and never stores or has access to your health data.

Why it exists

Demo

Demo video coming. Here's what a typical conversation looks like:

You:     How was my recovery this week? Anything standing out?

Claude:  Your recovery this week was mixed but trending positive.
         • HRV averaged 58ms (Tue–Thu strong at 64–68ms; Monday low at 44ms after Saturday's long run)
         • Sleep averaged 7h 12m — Wednesday and Thursday were your best nights (7h 40m+)
         • Resting HR dropped from 54bpm Monday to 49bpm Friday — a good sign
         Recommendation: today looks like a solid day for a moderate-intensity session.

Quick start

health4ai needs a Supabase project you own. The app signs in with Supabase Auth and writes through a Supabase Edge Function, so plain Postgres (Neon, a local Docker container) is not a supported backend. Full walkthrough: docs/SETUP.md.

1. Create the schema. Create a project at supabase.com, open its SQL editor, and run web/public/schema.sql (also at https://health4.ai/schema.sql). It is generated from supabase/bootstrap/: tables, row-level security, and grants that deny clients direct access. Do not use supabase db push — the numbered migrations do not apply to a fresh project.

2. Deploy the ingest function (needs the Supabase CLI):

git clone https://github.com/jefflitt1/health4ai.git
cd health4ai
supabase functions deploy healthkit-ingest --project-ref <your-project-ref> --no-verify-jwt

--no-verify-jwt is deliberate: the function verifies the signed-in user's token itself and writes only under that user's ID.

3. Create your user. In the dashboard, Authentication → Users → add a user, and copy its UID. The app signs in; it does not sign up.

Then set up the MCP server (from the same checkout):

cp mcp-server/.env.example mcp-server/.env

Edit mcp-server/.env:

DATABASE_URL=postgresql://...  # your project's pooler connection string (database password, not a key)
HEALTHKIT_USER_ID=...           # your Supabase Auth user's UID (see mcp-server/.env.example)

Add to your AI client:

{
  "mcpServers": {
    "health4ai": {
      "command": "python",
      "args": ["/path/to/health4ai/mcp-server/main.py"],
      "env": {
        "DATABASE_URL": "postgresql://...",
        "HEALTHKIT_USER_ID": "<your auth user UID>"
      }
    }
  }
}

mcphost --model ollama/llama3.2 \
  --mcp-server "health4ai:python /path/to/health4ai/mcp-server/main.py"

Install the iOS app from the App Store, then connect it to that Supabase project (Project URL + anon key), sign in as the user you created, and tap Start Sync. For a TestFlight beta build, follow the tester-isolation guide; never use another person's backend or credentials.

MCP tools

If a metric is empty, read data_status before believing it

iOS never tells an app that a Health permission was denied. A type you have not shared returns an empty result, byte-for-byte identical to a day where you genuinely did nothing. Nothing in HealthKit's API can distinguish the two, so an assistant reading a bare 0 will confidently tell you that you took no steps.

Tools that can return an empty result therefore attach a data_status block:

• never_recorded — this metric has never produced a sample for you. For steps, heart rate, active energy or walking distance that is not possible if the data were being shared, so it almost certainly is not. Open Health → Sharing → Apps → health4ai, switch the metric on, then re-run the import from the app's Home tab.
• empty_window — nothing in the window you asked about, but the metric has data at other times. A real gap, not a permission problem.

This is not hypothetical. On the author's own account, step count, heart rate, active energy and walking distance were silently unshared for nearly three months while every other metric synced normally, and the app displayed a green "Complete" throughout.

Architecture

┌─────────────────────────────────────────────────────────────┐
│  iPhone                                                      │
│  HKObserverQuery + BGTaskScheduler                          │
│  → continuous background sync                               │
└──────────────────────────┬──────────────────────────────────┘
                           │ HTTPS → your healthkit-ingest Edge Function
                           ▼
┌─────────────────────────────────────────────────────────────┐
│  Your Supabase project (you own it)                         │
│  healthkit_metrics · healthkit_daily_summaries              │
│  row-level security on · no direct client access            │
└──────────────────────────┬──────────────────────────────────┘
                           │ Postgres connection (database password, from your machine)
                           ▼
┌─────────────────────────────────────────────────────────────┐
│  FastMCP server  (mcp-server/main.py)                       │
│  FastMCP tools · stdio transport                             │
└──────────────────────────┬──────────────────────────────────┘
                           │ MCP
                           ▼
              Claude · ChatGPT · Cursor · Ollama · any client

Data tiers: queries within the last 30 days return raw samples. Older days use a pre-aggregated row from healthkit_daily_summaries where one exists and are otherwise aggregated per day inside Postgres from the raw samples, so results are complete whether or not the summariser has ever run on your project (on a fresh self-hosted project it never has). Responses carry a tier block saying how many days each tier served. Calendar days follow HEALTH4AI_TZ (default UTC; set it in mcp-server/.env).

Repo structure